JP3151048B2 - Polygon mirror mounting structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting structure of a polygon mirror applied to an image forming machine, for example, a laser beam printer.

[0002]

2. Description of the Related Art A polygon mirror conventionally used for a laser beam printer is attached to, for example, a shaft of a hall motor and rotates at a high speed. Also, its rotation speed,
The speed is accurately controlled by the control device. The polygon mirror is made by cutting from an aluminum material, and a polygonal portion formed on an outer peripheral portion thereof constitutes a mirror surface.
In a laser printer, when a rotating polygon mirror is irradiated with a semiconductor laser beam whose light intensity has been modulated, this laser beam is reflected in different directions depending on the position of the mirror surface at that moment. As a result, the surface of the photosensitive drum is scanned with the reflected light, and a latent image of print information is formed. The latent image is then developed with toner,
The transfer and fixing actions take place and appear on the medium.

The attachment of the polygon mirror to the shaft of the motor has been performed, for example, by screwing the polygon mirror to the shaft. According to this mounting structure,
A through-hole must be formed in the polygon mirror itself, and a screw must be formed in the inner periphery thereof. This requires many processing steps, and is not suitable for mass production, and the cost is high. It is necessary to use an adhesive or the like to prevent the screw connection from loosening, and the assembling workability is not good. Further, the polygon mirror may be damaged during the work of tightening the shaft. As another mounting structure, a holding preload spring for holding a polygon mirror and a C-ring for fixing the same, or a combination of a holding preload spring, a cup and a screw for fixing the same are used. According to these mounting structures, similarly, the number of parts increases and workability is poor. On the other hand, since the rotor is rotated at a high speed of 10,000 rotations or more, slight imbalance, which is not a problem at low speed rotation, or insufficient pressing force for pressing the polygon mirror against the hub causes vibration of the polygon mirror. Adversely affect the accuracy of Therefore, it is desired that the number of parts on the rotor side is as small as possible. However, according to the conventional polygon mirror mounting structure, since the number of parts is relatively large, the possibility of the vibration is extremely high. There is a problem that the reliability at the rotation speed or higher is not sufficiently guaranteed.

[0004]

SUMMARY OF THE INVENTION The main object of the present invention is to provide an improved polygon mirror mounting structure which has a small number of parts and can reliably suppress vibration of the polygon mirror during high-speed rotation. is there.

[0005]

According to the present invention, there is provided a hub which is rotated by a driving force of a motor, and which is fitted and mounted on an outer peripheral portion at one axial end of the hub. A polygon mirror, and a spring member for holding the polygon mirror in a mounting position, a boss portion protruding in the axial direction is formed on the one end side of the hub, and at least a portion around the boss portion is formed on the hub. A fitting groove means is formed, the spring member is formed of an annular plate member, a protruding means for fitting into the fitting groove means is formed on an inner peripheral portion thereof, and an outer peripheral portion thereof is provided along a circumferential direction. Further, a plurality of pressing portions are formed, which are gradually downwardly inclined in the rotation axis direction toward the rotation direction of the hub, and each of the pressing portions is formed of a bent portion that protrudes in the axial direction, and the spring member is Fitting the projecting means into the fitting groove means Each of the bent portions provided on the holding portion presses the polygon mirror in the axial direction of the hub, and when the hub rotates, each of the holding portions increases the pressing force on the polygon mirror due to an air flow. A mounting structure for a polygon mirror is provided.

[0006]

When the hub rotates at a high speed in a state where the polygon mirror is fitted and mounted on the outer peripheral portion of the hub by the spring member, air passes at high speed over each upper surface of the pressing portion of the spring member. By this high-speed airflow, a force for pressing the polygon mirror in the axial direction is applied to each of the holding portions. This force increases as the rotation speed of the rotor increases, and the polygon mirror is more firmly pressed against the hub, so that vibration during high-speed rotation is reliably prevented. Also, the spring member is pushed into the hub from the axial direction or simply rotated after being pushed, the protruding means is fitted and held in the fitting groove means of the hub, and each of the holding parts holds the polygon mirror. Since it is configured to be pressed in the axial direction of the hub, the work of attaching the polygon mirror is easy.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a mounting structure of a polygon mirror according to the present invention.

1 to 4 showing an embodiment in which the present invention is applied to an axial flux type brushless DC motor, the mounting structure of a polygon mirror includes a hub 14, a polygon mirror 36 and a spring member 46 which will be described in detail later. In. Reference numeral 2 denotes a fixed base of the motor, and a shaft 4 indicated by a two-dot chain line is fixed upright at a central portion thereof. An armature coil 6 is annularly arranged on the upper surface of the fixed base 2 on the fixed shaft 4 side. A rotor 8 is rotatably supported on the fixed shaft 4 via a bearing (not shown). The rotor 8 includes a rotor base 10, a rotor magnet (permanent magnet) 12 mounted on the lower surface side of the rotor base 10,
And a hub 14 mounted on the upper surface side of the rotor base 10. The rotor magnet 12 is positioned to face the armature coil 6 at a predetermined interval in a plane. A magnet 16 for a frequency oscillator for detecting a rotation speed of the rotor 8 is mounted on an outer peripheral portion of the rotor base 10, while a pickup coil 18 is mounted on an upper surface of the fixed base 2. Pickup coil 1
Numeral 8 is positioned to face the magnet 16 at a predetermined interval in a planar manner.

The hub 14 is formed in a cup shape from aluminum. A through hole 22 is formed in the axial center of the wall 20 that defines one end of the hub 14, and is rotatably fitted and supported on the fixed shaft 4 of the motor via a bearing (not shown). Thus, the rotor 8 is rotatably supported by the fixed shaft 4 of the motor. The hub 14 has an outer peripheral portion 24 to which a polygon mirror 36 described later is fitted and mounted. The outer peripheral portion 24 has a circular cross section and extends in the axial direction from one end of the hub 14, and the other end is defined by a shoulder (step portion) 26. The shoulder 26 has a right angle surface extending radially outward from the outer peripheral portion 24. A boss 28 protruding in the axial direction is formed on one end of the hub 14. At least a part of the periphery of the boss portion 28 is formed with a fitting groove means. That is, as shown in FIGS. 1 and 4, a predetermined cross-sectional shape (a spline shape in this example) is provided around the boss portion 28.
Are formed. Numeral 30 indicates a concave portion, and numeral 32 indicates a convex portion. Each of the protrusions 32 is formed with a fitting groove 34 having an arc shape centered on the axis of the hub 14. The fitting groove means is constituted by a fitting groove 34 in this embodiment. The outer diameter of the boss portion 28 is smaller than that of the outer peripheral portion 24, and there is a predetermined gap between the fitting groove 34 and the shoulder 26 in the axial direction.

A polygon mirror 36 is fitted and mounted on the outer peripheral portion 24 of the hub 14. The polygon mirror 36 has a polygonal outer peripheral portion 38 and the hub 1 as clearly shown in FIG.
Hole 40 having an inner peripheral shape capable of fitting to outer peripheral portion 24 of hole 4
And both axial side surfaces 42 and 44 defined by a surface orthogonal to the axis. The polygon mirror 36 is formed of aluminum, and each surface of the polygon forms a mirror surface. The cross-section of the outer peripheral portion 24 of the hub 14 is circular in the illustrated example, but may be a cross-sectional shape that does not allow relative rotation with the mating partner. In this case, the hole 40 of the polygon mirror 36 has an inner peripheral shape that can be fitted therein.

A spring member 46 holds the polygon mirror 36 at a mounting position. The spring member 46 is formed from an annular plate member (for example, phosphor bronze, a spring steel plate, or a synthetic resin). As shown in FIG. 2, a projecting means that can be fitted in the fitting groove means is formed on the inner peripheral portion of the spring member 46. That is, on the inner peripheral portion of the spring member 46, an uneven portion having a shape capable of fitting with the uneven portion of the boss portion 28 is formed. Numeral 48 indicates a concave portion, and numeral 50 indicates a convex portion. The protruding means is constituted by the concave and convex portions (48, 50) in this embodiment. A plurality of pressing portions 52 are formed on the outer peripheral portion.
Each of the pressing portions 52 is formed by punching a predetermined length in the circumferential direction, and the bent portion 5 protruding in the axial direction.
2 '. The spring member 46 holds the protruding means (50) in the fitting groove means (34) so that each of the pressing portions 52 connects the polygon mirror 36 to the hub 1.
4 is configured to be pressed in the axial direction. That is,
The inner peripheral surface of each of the concave and convex portions of the spring member 46 and the outer peripheral surface of each of the concave and convex portions of the boss portion 28 are formed in arcs centered on their axes. The uneven portion of the spring member 46 is
8, the spring member 46 is aligned.
Of the boss portion 28 and the spring member 4
6 is pushed in the axial direction from one end side of the boss portion 28 and rotated in a state where the protrusion portions 50 of the boss portion 28 are respectively aligned with the recess portions 30 of the boss portion 28, so that each of the protrusion portions 50 of the spring member 46 Grooves 3 formed in each of the convex portions 32
4 is held. At the same time, each of the pressing portions 52 is configured to press the polygon mirror 36 in the axial direction of the hub 14. In this mounting state, each of the holding portions 52 has a bent portion 52 ′ at the tip thereof,
1 and is arranged in the direction of rotation of the hub 14 (the direction of the arrow in FIGS. 1 and 2).
The blade 4 has a blade shape such that the pressing force on the polygon mirror 36 is increased by the airflow accompanying the rotation of 4.

A polygon mirror 36 is fitted to the outer peripheral portion 24 from one end of the hub 14, and is mounted with the side surface 44 pressed against the shoulder 26. Next, the boss portion 28 is adjusted in a state where the uneven portion of the spring member 46 is aligned with the uneven portion of the boss portion 28.
When one end is pushed in the axial direction and rotated by a predetermined angle, each of the protrusions 50 of the spring member 46 is fitted and held in each of the fitting grooves 34 of the boss 28 (so-called bayonet connection). . This prevents the spring member 46 from coming off the hub 14 in the axial direction. At the same time, the pressing portion 52 that comes into contact with one side surface 42 of the polygon mirror 36 is bent with the convex portion 50 fitted into each of the fitting grooves 34 as a fulcrum. As a result, each of the pressing portions 52 of the spring member 46 presses the polygon mirror 36 in the axial direction of the hub 14, specifically, presses the side surface 44 of the polygon mirror 36 against the shoulder 26. The member 46 is securely attached to the hub 14 only by pushing and rotating the member 46 in the axial direction. When the armature 6 is energized, the rotor 8 rotates around the fixed shaft 4 at a predetermined rotation speed. The polygon mirror 36 is rotated together with the hub 14 together therewith. Since the rotor 8 rotates at high speed, air is generated by the spring member 46.
At a high speed. By this high-speed airflow, a force for pressing the polygon mirror 36 in the axial direction (toward the shoulder 26) is applied to each of the pressing portions 52. This force increases as the rotation of the rotor 8 increases, and the polygon mirror 36 is more firmly pressed against the hub 14, so that vibration during high-speed rotation is reliably prevented. The number of rotations of the rotor 8 is detected by the frequency oscillator magnet 16 and the pickup coil 18. A control device (not shown) accurately controls the rotation speed of the rotor 8 based on this detection information. FIG. 5 shows the hub 14.
FIG. 9 is a cross-sectional view showing a state where the polygon mirror 36 is incorporated into the hub 14 and the polygon mirror 36 is fixed to the hub 14 by a spring member 46.

Next, another embodiment in which the present invention is applied to an outer-rotor brushless DC motor in which a fixed armature coil and a rotor magnet are circumferentially opposed to each other will be described. 6 to 10 showing another embodiment of the present invention, the mounting structure of the polygon mirror includes a hub 60, a polygon mirror 74, and a spring member 84, which will be described in detail later. The hub 60 is formed in a cup shape from a synthetic resin, and a magnet (permanent magnet) 61 for a motor is embedded in an inner portion formed in the cup shape. Hub 6
0, a through hole 64 is formed in the axial center of the ceiling 62 defining the upper surface.
Is formed, and a fixed shaft (not shown) penetrates. Through hole 64
A bearing (not shown) is interposed between the side wall and the fixed shaft, whereby the hub 60 rotates as a rotor of the motor. The hub 60 has an outer peripheral portion 66 to which a polygon mirror 74 described later is fitted and mounted. Outer circumference 66
Has a circular cross section and extends in the axial direction from one end of the hub 60,
The other end is defined by a shoulder (step) 68. The shoulder 68 comprises a right angled surface extending radially outward from the outer periphery 66. A boss 70 protruding in the axial direction is formed on the one end side of the hub 60. Fitting groove means is formed around the boss 70. That is, an annular fitting groove 72 is formed around the boss 70 around its axis. The outer diameter of the boss portion 70 is smaller than that of the outer peripheral portion 66, and there is a predetermined interval in the axial direction between the fitting groove 72 and the shoulder 68.

A polygon mirror 74 is fitted and mounted on the outer peripheral portion 66 of the hub 60. As clearly shown in FIG. 8, the polygon mirror 74 includes a polygonal outer peripheral portion 76 and a hub 6.
Hole 78 having an inner peripheral shape that can be fitted to the outer peripheral portion 66
And both axial side surfaces 80 and 82 defined by a surface orthogonal to the axis. The configuration of the polygon mirror 74 is the same as that of the polygon mirror 3 described in the previous embodiment.
6, the description will be omitted.

A spring member 84 holds the polygon mirror 74 at the mounting position. The spring member 84 is formed from an annular plate member (for example, phosphor bronze, a spring steel plate, or a synthetic resin). A projecting means which can be fitted in the fitting groove 72 which is a fitting groove means is formed on the inner peripheral portion of the spring member 84. That is, the projecting means is, in this embodiment,
A plurality of engaging claws 86 formed on the inner periphery of the spring member 84
It is composed of A plurality of pressing portions 88 are formed on the outer periphery. Each of the engaging claws 86 is formed by bending an axially protruding tip portion in the axial direction. Each of the pressing portions 88 is formed by punching a predetermined length in the circumferential direction and formed by a bent portion protruding in the axial direction. The projecting direction of the pressing portion 88 is opposite to that of the engaging claw 86. The spring member 84 has its protruding means (86) connected to the fitting groove means (72).
Each holding portion 88 is configured to press the polygon mirror 74 in the axial direction of the hub 60 by fitting and holding the polygon mirror 74. That is, by pushing the spring member 84 in the axial direction from one end side of the hub 60, each of the engaging claws 86 is fitted and held in the fitting groove 72 of the hub 60. At the same time, each of the pressing portions 88 is configured to press the polygon mirror 74 in the axial direction of the hub 60. The configuration of each of the pressing portions 88 is substantially the same as that of the pressing portion 52 described in the previous embodiment, and the description thereof will be omitted.

A polygon mirror 74 is fitted to the outer peripheral portion 66 from one end of the hub 60, and is mounted with the side surface 82 pressed against the shoulder 68. Next, the spring member 84 is connected to the hub 6.
When one end of the hub 0 is pushed in the axial direction, each of the engaging claws 86 of the spring member 84 is fitted and held in the fitting groove 72 of the hub 60 by a spring action. As a result, the spring member 84
It is prevented from coming off the hub 60 in the axial direction. At the same time, the holding portion 88 that contacts one side surface 80 of the polygon mirror 74 is bent. As a result, with each of the engagement claws 86 fitted in the fitting groove 72 as a fulcrum, the pressing portion 88 of the spring member 84 is used.
Each presses the polygon mirror 74 in the axial direction of the hub 62. Specifically, the side surface 82 of the polygon mirror 74 is
6, the polygon mirror 74 is moved by the spring member 8
4 can be securely attached to the hub 60 only by pushing in the axial direction. When an armature (not shown) of the motor is energized, the hub 60 rotates around a fixed axis at a predetermined rotation speed. The polygon mirror 74 is rotated together with the hub 60 together therewith. Since the hub 60 rotates at high speed,
The air passes at high speed over each upper surface of the holding portion 88 of the spring member 84. With this high-speed air flow, the polygon mirror 74 is moved in the axial direction (toward the shoulder 68) for each of the holding portions 88.
Is applied. This force increases as the rotation of the hub 60 increases, and the polygon mirror 74 is
Since it is more firmly pressed against zero, vibration during high-speed rotation is reliably prevented. FIG. 10 is a partial cross-sectional view showing a state where the polygon mirror 74 is incorporated in the hub 60 and the polygon mirror 74 is fixed to the hub 60 by the spring member 84.

The present invention has been described with reference to one embodiment.
Various modifications are possible within the scope of the present invention, and these are not excluded from the scope of the present invention.

[0018]

According to the present invention described above, the number of parts is small, and the vibration of the polygon mirror during high-speed rotation can be suppressed reliably. As a result, the accuracy of scanning by the polygon mirror can be reliably maintained, and the reliability can be sufficiently ensured. Since the holding force of the polygon mirror increases as the rotation speed increases, there is no possibility that the initial set value of the spring force of the spring member is set to be excessively large.
Also, the polygon mirror can be firmly held on the hub simply by pushing the spring member in the axial direction from one end of the hub, or simply by pushing and rotating the hub. I do. Further, since there is no possibility of damaging the polygon mirror, quality and reliability are improved. Furthermore, since the number of parts is small, mass production can be performed at low cost.

[Brief description of the drawings]

FIG. 1 is an exploded view showing an essential part of an embodiment of a mounting structure of a polygon mirror improved according to the present invention, with a part cut away.

FIG. 2 is a plan view of the spring member shown in FIG. 1;

FIG. 3 is a plan view of the polygon mirror shown in FIG. 1;

FIG. 4 is a plan view of the hub shown in FIG. 1;

FIG. 5 is a partial sectional view showing a state in which a polygon mirror is attached to a hub and fixed by a spring member.

FIG. 6 is an exploded view showing a main part of another embodiment of the mounting structure of the polygon mirror improved according to the present invention,
Figure showing partly broken

FIG. 7 is a plan view of the spring member shown in FIG. 6;

FIG. 8 is a plan view of the polygon mirror shown in FIG. 6;

FIG. 9 is a plan view of the hub shown in FIG. 6;

FIG. 10 is a partial cross-sectional view showing a state where a polygon mirror is attached to a hub and fixed by a spring member.

[Explanation of symbols]

 14 and 60 hubs 24 and 66 outer peripheral portions 26 and 68 shoulders 30 concave portions 32 convex portions 34 fitting Grooves 36 and 74 Polygon mirrors 46 and 84 Spring members 48 Concave portions 50 Convex portions 52 and 88 Holding portions 72 ... Mating groove 86 ...

────────────────────────────────────────────────── (5) References JP-A-54-108646 (JP, A) JP-A-61-175612 (JP, A) JP-A-4-51073 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) G02B 26/10

Claims (3)

(57) [Claims] 1. A hub which is rotated by a driving force of a motor, a polygon mirror fitted and mounted on an outer peripheral portion at one axial end of the hub, and a spring member for holding the polygon mirror at a mounting position. , On the one end side of the hub,
A boss protruding in the axial direction is formed, a fitting groove means is formed in at least a part of the periphery of the boss, the spring member is formed of an annular plate member, and the inner peripheral portion has the fitting member. A plurality of pressing portions are formed on the outer peripheral portion of the projecting portion to be fitted into the groove means, and a plurality of pressing portions are formed along the circumferential direction and gradually descend and incline in the rotation axis direction toward the rotation direction of the hub. Each tip of the spring member is constituted by a bent portion projecting in the axial direction, and the spring member has a bent portion provided on the holding portion by fitting and holding the projecting means in the fitting groove means. Pressing the polygon mirror in the axial direction of the hub,
The mounting structure of a polygon mirror, wherein when the hub rotates, the pressing force on the polygon mirror increases in each of the pressing portions due to an air flow. 2. A plurality of concavo-convex portions having a predetermined cross-sectional shape are formed around the boss portion, and the fitting groove means includes:
The protrusions of the spring member are formed by arc-shaped fitting grooves centered on the axis of the hub formed on each of the protrusions. The spring member is constituted by a concave and convex portion that can be fitted, and is pushed in the axial direction from the one end side of the hub and rotated in a state where the concave and convex portion of the spring member is aligned with the concave and convex portion of the boss portion. 2. The polygon mirror mounting structure according to claim 1, wherein each of the protrusions is fitted and held in each of the fitting grooves of the boss. 3. The fitting groove means comprises an annular fitting groove formed around the boss portion and centered on the axis of the hub, wherein the projecting means of the spring member includes Each of the engaging claws is fitted into the fitting groove of the hub by pushing the spring member in the axial direction from one end side of the hub. The mounting structure of the polygon mirror according to claim 1, wherein the mounting structure is configured to be held.